Photonic circuitry is often etched onto integrated circuits that are used in communication networks. The waveguides and other components of such circuits transmit and modify optical data pulses. Unlike communication networks that use conventional conductors and the transmission of electrical pulses that can navigate the turns and bends of the conductor, optical pulses in a waveguide cannot make such tight turns and bends without unacceptable losses via attenuation and escape. Because of this inability of optical pulses to make tight turns and bends in a waveguide, it is problematic to design and manufacture photonic multi-layer integrated circuits. While it has been postulated that micro-mirrors be used to change the direction of a light path in a photonic circuit, the use of mirrors in integrated circuits poses several manufacturing and application problems.
Photonic circuitry and communication networks would benefit if optical pulses could be routed in directions that would allow multiple vertically disposed layers of integrated circuitry to be reliably connected. Such connections would require bends in the path of the light pulses, which cannot take place unaided in a typical waveguide.